docs: def to_bel_lines(graph) -> Iterable[str]:
      """Iterate over the lines of the BEL graph as a canonical BEL Script (.bel).
  
      :param pybel.BELGraph graph: the BEL Graph to output as a BEL Script
      """
      return itt.chain(
          _to_bel_lines_header(graph),
          _to_bel_lines_body(graph),
          _to_bel_lines_footer(graph),
      )